Talk about a brilliant marketing event: free pizza will be handed out to thousands of people attending 4/20 rallies in three Canadian cities this weekend.

JUST-EAT.ca, an online food ordering service, is organizing the so-called pizza mob on Sunday at 4:20 p.m. local time at the Vancouver Art Gallery, Dundas Square in Toronto, and Parliament Hill in Ottawa.

April 20 is an unofficial holiday for marijuana enthusiasts, with many gathering to consume bud together.

The company plans to "descend upon hungry, red-eyed crowds right around 4:20 p.m. and offer fresh, piping hot slices of pizza to those celebrating the 'green' holiday," said a news release on Thursday.

The pizza will be provided by Freshslice, Lorenzo’s and Pizza Shark.

The giveaway in Toronto, however, is being denied by a rally organizer, who says the marketer behind the event refused to pay cleanup fees.